Avoidance Reactions of Juvenile Coho Salmon (Oncorhynchus kisutch) to Monocyclic Aromatics

Presmolt coho salmon (Oncorhynchus kisutch) tested in a Y-maze avoided a mixture of monocyclic aromatic hydrocarbons at concentrations of 3–4 mg/L while smolting coho salmon avoided concentrations of less than 2 mg/L. Three components (benzene, toluene, o-xylene) of the mixture were tested individually with presmolt salmon and each was avoided at a lower concentration than when compared with the total hydrocarbon concentration of the mixture; o-xylene was most repellent, causing statistically significant avoidance at a concentration of 0.2 mg/L. Electrophysiological recordings from the olfactory bulb indicated that short-term exposure of juvenile coho salmon to monocyclic aromatic hydrocarbons at 4 mg/L did not disrupt this chemosensory modality; the olfactory system was stimulated by an aromatic hydrocarbon mixture at concentrations correlating with observed avoidance behavior.Key words: salmon, behavior, avoidance, monocyclic aromatic hydrocarbons, Oncorhynchus, olfactory EEG